If Dan was Charlie's brother wouldn't that make his last name Sheen and not Sanders? Or maybe even Estevez if they wanted to get technical. Lol if they would've made his last name Sheen he'd be a Dan Sheen fool.
I'm not sure why they changed the characters' names. In Scary Movie 3 (2003), Charlie Sheen and Simon Rex played Tom and George Logan. Apparently, in this one, they were playing Charlie and Dan Sanders. I know Charlie seemed to be playing a version of himself, but I don't remember ever saying his last name was supposed to be Sheen in this movie.
In the cast they show that that Charlie and Lindsey are playing themselves. All the references seem to indicate they were playing themselves as well. I think they were just making fun of all the trouble they were getting into. Just like a TV show where they have an actor playing themselves.